Acetyl-cellulose plastic



Patented Oct. 3, 1933 v V l i v I a UNITsosr rss rArsNT forties f j A QWPQEL SE A T JamesF. Walsh; East Orange, and'Amerigo F.

Caprio, Newark, N. 'J., assignors to Celluloid Corporation, a corporation of New Jersey No Drawing, Application ctober,l3, 1927 v Serial No. 225,016

4 Claims. (c1. iii-4.8)

The practice heretofore has been to mix the the film wheel apparatuspreferable for it accellulose acetate with sufiicient plasticizer and complishes solvent recovery-without hazardto liquid solvent to make the compositionoi fa palen-ess of hue and furnishes the evaporated dough-like consistency workable in a kneader product in a handy form. In fact, such are the 1 5 or pair of rolls. This required about 60 to 100 peculiar advantages of the film process asa step .69 parts of liquid solvent to the hundred of acetate, in our operations that its effect extends {in a also sufiicient plasticizer forthe desired degree certain degree to the manipulation off-solutions, of final hardness or moldability. The gelatinous oi pyroxyiin as well as those of the acetate, Our mixture is allowed to soak in a warm room-for a film is not always removed from the wheel in 110 day or so and is then filtered under heavy presthe same condition of dryness, for the reduced 5 sure. This processof solution and manipulation 'solventrcontent must correspond tothe require; has peculiar disadvantages inthat the'completed merits of the next operations-'-those of colorproduct, say planed sheeting, is of somewhat inihg and solidification. If, for. example, the ferior strength or tenacity and-more or less liable prpduct is to be coloredor given a special shaping to contain dirt and undissolved fiber which perin rolls the solvent content will ccrrespondin' .70 v

'sist in spite of repeated filtering operations. degree to that or the dough like masses According to our invention, which is the result the usual process at the. roll stage, allowance of many attempts to secure an acetyl-cellulose of course being made for the more adaptable plastic comparable with one made of pyroxylin, condition of our mixtures. For having received .20 or even excelling it, we get better conversion in 'a superi 2: conversion by means of our liquidI-Ei the dissolving and solidifying operations, with method, the film product does not nee'd the resultant strength and tenacity of superior charusual smoothing and evening-up work but is acter, also perfect freedom from dirt and unready for quick manipulation. Hence at this dissolved fiber, by substituting the fiow process point our residual proportion or contact of liquid of conversion for the first stages of prevailing solvent is appreciably'less than that required for 80 operations. I rolling the cellulose acetate mixtures prepared To accomplish this we dissolve the acetyl celby the dough method. To give exact proporlulose in enough liquid solvent, say 350 to 450 tions would. be uninstructive except for a parparts, to make a mass flowable in the cold as ticular instance. The experienced. operator as- 3Q distinguished from the usual dissolving which certains the proportions for himself, merely asso- 3-5 employs so little solvent that heat or warmth ciating definitefigures with definite conditions and mechanical means are required for a positive and purposes; as, for example the viscosity of his; change of shape in the mass. In other words, acetyl-cellulose, the influence of the plasticizer, our first stage of mixture is a so-called dope sufand the required time of exposure to the air ficiently liquid to be spread on surfaces with a when adding colors or shaping certain configura- .9 scraper to form thin films, whereas the usual tions. ivi'anycolors can be combined with our primary stage of mixing produces a mere dough mixtures while said mixtures are still in flowor stiff paste. r I able condition. This applies particularly to" The first effect of our abundant use of solvent dyes. But in general we prefer the addition of.

fi is an almost complete conversion of the acetate color or pigment at the rolls, or if the amount 25 fiber-a conversion unattainable when operating is large, and requires much mixing, as in the with doughlike solutions in arkneader or on rolls. case of dense white, we use kneaders in which A second effect comes from the semi-liquid conevent the amount of residual solvent must be dition of our mixture, which condition makes it suited to kneaderaction requirements. In a so susceptible to straining that the insolubles case of heavy pigmentation, such as the one just .100 are held back completely and are not disposed mentioned, it is sometimes well to combine the to pass through the filter cloth like similar par pigment with the flowable mixture by kneader tides in t usual hlike masses. action before proceeding to recover the excess Having attained good conversion and cleanlisolvent either in the same apparatus or bytransness we reduce our fiowable solution of the fer to film-wheel mechanism. Our experience, 1 05 acetate to a condition suitable for manipulation however, hasdemonstrated that even such pigin rolls and presses to form a solid material. ments as zinc oxide in copious proportions can To secure this efiect we may. in some cases ernbe combined with the ,dope in the usual dope ploy a so-called vacuum kneader or other'means, mixingtanks and that subsequent filtration per of evaporation, but in practice we have found fects the combination. a v ilo.

After the roll operation our mixtures are prepared for the making of sheets or other form by subjection to the usual solidification operations attained by mechanism which employs heat and pressure, The essential feature of our invention is the formation of a fiowable dope mixture which is readilyand efficiently filtered, and which, because of such a state, gives a finished product of improved strength and uniformity creme" ture.

Our enhancement of strength .in acetyl-cellu-, lose products constitutes an important advance in the art and we accomplish-this and freedom" from impurities by means developed, through much experimentation. Our preferred process has such unique features that it is applicableto the making of nitro-cellulosecompounds as well readily filtered, filtering the solution while in a condition so'nearly approaching liquidity that substantially all impurities and other insoluble. materials are held back, stiffening the solution by removal of part of the solvent until a consistency suitable for roll manipulation is ob-' tained, then working the material between heated malaxating rolls, and then subjecting the material to an operation to complete the solidification thereof.

2. The process of making a plastic substance which comprises dissolving a cellulose ester in a suitable amount of volatile solvent so as substantially to completethe conversion of the cellulose ester to form a solution that may be readily filtered, filtering the solution while in a condition so nearly approaching liquidity that im-' purities are readily removed, forming it into partly dry films by casting the solution on' a surfaceand causing part of the volatile solvent to evaporate, then working the films between heated *rolls to remove further quantities of volatilesolvent, and finally subjecting the resulting material to heat and pressure to solidify it. 3. The process-of making a plastic substance which comprises dissolving cellulose acetate in a"suff1cientamount of volatile solventrto form a freely fiowingsolution, subjecting the solution to a thorough filtration to remove the undissolved impurities, forming partly dry films from such solution" by casting the same on a surface and causing part of the volatile solvent to evaporate, adding-color or, pigment to the partly dry films, and then working-the films between heated rolls to remove further quantities of volatile" solvent. "*fi-I he processof -making a plastic substance I which comprises dissolving cellulose acetate in 1 0 alsufiicientquantity of volatile solvent to form a lflowab'le solution, subjecting the' solution to a thorough'filtrationto'remove the undissolved impurities, forming thesam into partly dry films by flowing or spreading the solution and 105 causing part of the volatile solvent to evaporate,

'niassing' th efilms, and then; subjecting the massed films to manipulation or solidification ,op-

erations by 'rolling, pressing or equivalent formative steps.

JAMES FuWALSH;

'AMERIGQ F. CAPRIO. 

